Seal structure and centrifugal compressor

ABSTRACT

Provided is a seal structure ( 50, 60 ) configured to seal a clearance ( 31, 32 ) with respect to a flow path defined by a rotary body ( 20 ) rotated about a central shaft (P) and configured to allow passage of a mainstream, and a stationary body ( 10 ) disposed at the rotary body ( 20 ) to form the clearance ( 31, 32 ), the seal structure including a seal member ( 51 A,  51 B) installed at the clearance ( 31, 32 ) and configured to divide a fluid introduced from the mainstream into the clearance ( 31, 32 ) into a high pressure side and a low pressure side, and a shifting member ( 52 A,  52 B) installed at the high pressure side of the fluid in the clearance ( 31, 32 ), and configured to allow passage of the fluid and reduce a velocity component in a rotational direction of the rotary body ( 20 ) of the velocity component of the fluid.

TECHNICAL FIELD

The present invention relates to a seal structure and a centrifugalcompressor.

This application claims priority to and the benefit of Japanese PatentApplication No. 2010-201803 filed on Sep. 9, 2010, the disclosure ofwhich is incorporated by reference herein.

BACKGROUND ART

As is well-known, in a multi-stage centrifugal compressor, a rotor inwhich a plurality of impellers are attached to a rotary shaft isprovided, and a U-shaped flow path having a substantially U-shapedcross-section in which two neighboring impellers are in communicationwith each other in an axial direction in a casing which is configured toaccommodate the rotor is provided, so that the pressure of a mainstreamof working gas is increased as it goes from upstream to downstream.

In the multi-stage centrifugal compressor, for example, a clearance isformed between an inner partition wall configured to partition a flowpath into a low pressure side (a U-shaped flow path of an upstream side)and a high pressure side (a U-shaped flow path of a downstream side) ofa mainstream, and the impeller configured to pass through the mainstreamand supply energy. In order to seal the clearance, a seal member (forexample, a labyrinth seal) is installed.

In the multi-stage centrifugal compressor having the seal member, sincea fluid having a circumferential velocity component, which becomes aswirl flow, applies an exciting force to the rotor when passing throughthe seal member, the rotor may be unstably vibrated. As a result, noisemay be generated, or damage due to a contact between the rotor andperipheral parts may occur.

In the following Patent Document 1, a high pressure fluid is suppliedfrom a diffuser section of the U-shaped flow path to the seal memberdisposed at the inner partition wall configured to partition thediffuser section. More specifically, a fluid passage in communicationwith the diffuser section and the seal member is formed at the innerpartition wall, a high pressure fluid in the diffuser section issupplied to the seal member, and thus the exciting force negating theswirl flow and applied to the rotor is suppressed.

RELATED ART DOCUMENT Patent Document

[Patent Document 1] Japanese Unexamined Patent Application PublicationNo. 2003-148397

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, in the related art, since a fluid passage should be formed inthe inner partition wall, the configuration becomes complicated and theprocessing requires effort.

In consideration of the above-mentioned circumstances, the presentinvention is provided to reduce effort needed for the processing bysuppressing the exciting force and simplifying the configuration.

Means for Solving the Problems

A seal structure according to the present invention for sealing aclearance between a rotary body rotated around an axis and a stationarybody disposed adjacent to the rotary body, in which a main stream of afluid passes through a passage formed by the rotary body and thestationary body, the seal structure including: a seal member installedat the clearance and configured to divide a fluid flowed into theclearance from the mainstream into a high pressure fluid and a lowpressure fluid; and a shifting member installed at an area of the highpressure fluid in the clearance, and configured to allow passage of thefluid and reduce a velocity component in a rotational direction of therotary body in the velocity component of the fluid.

According to the above-mentioned configuration, since the shiftingmember installed at the high pressure side of the fluid in the clearancebetween the rotary body and the stationary body and configured to allowpassage of the fluid and reduce the velocity component in the rotationaldirection (hereinafter, simply referred to as a normal rotationaldirection) of the rotary body is provided, the velocity component in thenormal rotational direction of the fluid passing through the shiftingmember and arriving at the seal member is reduced. Accordingly, sincethe fluid passes the seal member in a state in which the velocitycomponent in the normal rotational direction is reduced, an excitingforce applied to the rotary body can be suppressed.

Further, since the exciting force applied to the rotary body issuppressed by installing the shifting member, in comparison with thecase in which a fluid passage is formed at the stationary body, theconfiguration can be simplified and an effort needed for the processingcan be reduced.

In addition, when the fluid passage is formed at the stationary body andthe high pressure fluid is supplied to the seal member, since adifferential pressure between the high pressure side and the lowpressure side of the fluid divided by the seal member is increased,while an amount of the fluid passing through the seal member isincreased, according to the above-mentioned configuration, since thedifferential pressure is reduced in comparison with the case in whichthe high pressure fluid is supplied to the seal member, the fluidpassing through the seal member can be suppressed to a small amount.

Further, the phrase “the velocity component in the rotational directionis reduced” is used to mean that the velocity component in rotationaldirection becomes a negative value in addition to approaching 0.

In addition, the shifting member may apply a velocity component in areverse direction of the rotational direction to the fluid.

According to the above-mentioned configuration, since the shiftingmember applies the velocity component in the reverse direction of thenormal rotational direction to the fluid, the velocity component in thenormal rotational direction of the fluid can be further reduced, and theexciting force applied to the rotary body can be further suppressed.

Further, the shifting member may be installed at a fluid inlet sectioninto which the fluid flows from the mainstream side to the clearance.

According to the above-mentioned configuration, since the shiftingmember is installed at the fluid inlet section, the velocity componentin the normal rotational direction of the fluid from the fluid inletsection toward the seal member can be reduced by reducing the velocitycomponent in the normal rotational direction of the fluid uponintroduction into the clearance. Accordingly, the exciting forcegenerated when the fluid having the velocity component in the normalrotational direction passes between the seal members from the fluidinlet section is reduced, and the exciting force generated upon passingthrough the seal member is reduced. Accordingly, the exciting forceapplied to the rotary body can be largely suppressed.

In addition, the shifting member is installed at the stationary bodyside.

According to the above-mentioned configuration, since the shiftingmember is installed at the stationary body side, an effect needed forthe processing can be further reduced without necessity of adjusting arotational balance of the rotary body like when the shifting member isinstalled at the rotary body side.

Further, the shifting member may have a passage block section formed atthe rotary body side and configured to block passage of the fluid, and ashifting section formed at the stationary body side, and having athrough-hole passing through the mainstream side and the seal memberside and formed at a position at which an aperture of the mainstreamside is slightly deviated in the reverse direction of the rotationaldirection with respect to an aperture of the seal member side.

According to the above-mentioned configuration, since the shiftingmember includes the passage block section configured to block passage ofthe fluid and the shifting section having the through-hole passingthrough the mainstream side and the seal member, the velocity componentin the reverse direction of the normal rotational direction can beapplied to the fluid through a simple configuration.

In addition, the shifting member may be installed at a position of theclearance in which the rotary body and the stationary body oppose eachother in the radial direction of the rotary body.

According to the above-mentioned configuration, since the shiftingmember is installed at a position of the clearance at which the rotarybody and the stationary body oppose each other in the radial direction,the velocity component in the normal rotational direction of the fluidcan be continuously reduced and an exciting force suppressing effect canbe stably obtained without variation in size of the clearance due to athrust force in the axial direction of the rotary body.

Further, a centrifugal compressor according to the present inventionhaving a flow path defined by the rotary body and the stationary body,wherein the rotary body comprises an impeller having a disc-shaped hub,a plurality of blades extending from the hub, and a shroud configured tocover outer circumferential ends of the plurality of blades, and thestationary body comprises a casing configured to accommodate theimpeller, and an inner partition wall configured to partition the flowpath into a low pressure side and a high pressure side of themainstream, the centrifugal compressor comprising: a seal structureaccording to any one of the above-mentioned configurations, the sealstructure configured to seal a first clearance formed between the shroudof the impeller and the inner partition wall.

In addition, the present invention provides a centrifugal compressorhaving a flow path defined by the rotary body and the stationary body,wherein the rotary body comprises an impeller having a disc-shaped huband a plurality of blades extending from the hub, and the stationarybody comprises a casing configured to accommodate the impeller, and anend partition wall configured to partition the inside and the outside ofthe casing, the centrifugal compressor comprising: a seal structureaccording to any one of the above-mentioned configurations, the sealstructure configured to seal a second clearance formed between the hubof the impeller and the end partition wall.

Further, the present invention provides a centrifugal compressor havinga flow path defined by the rotary body and the stationary body, whereinthe rotary body comprises an impeller having a disc-shaped hub, aplurality of blades extending from the hub, and a shroud configured tocover outer circumferential ends of the plurality of blades, and thestationary body comprises a casing configured to accommodate theimpeller, an inner partition wall configured to partition the flow pathinto a low pressure side and a high pressure side of the mainstream, andan end partition wall configured to partition the inside and the outsideof the casing, the centrifugal compressor comprising: a seal structureaccording to any one of the above-mentioned configurations, the sealstructure configured to seal a first clearance formed between the shroudof the impeller and the inner partition wall, and a second clearancebetween the hub of the impeller and the end partition wall.

According to the above-mentioned configurations, the exciting forceapplied to the rotary body can be suppressed and stably operated, andmanufacturing effort can be reduced.

In addition, in comparison with the case in which a high pressure fluidis supplied to the seal member, since a differential pressure betweenthe fluid high pressure side and the fluid low pressure side divided bythe seal member is reduced, the fluid passing through the seal membercan be suppressed to a small amount, and a volumetric efficiency can bemaintained to favorably maintain efficiency of the centrifugalcompressor.

Effects of the Invention

According to the seal structure according to the present invention, theeffort needed for the processing can be reduced by suppressing theexciting force and simplifying the configuration.

In addition, according to the centrifugal compressor according to thepresent invention, the exciting force applied to the rotary body can besuppressed and stably operated, and manufacturing effort can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a multi-stage centrifugalcompressor 1 according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of major parts of themulti-stage centrifugal compressor 1 according to the embodiment of thepresent invention, showing an enlarged view of a major portion I of FIG.1.

FIG. 3 is an enlarged cross-sectional view of major parts of themulti-stage centrifugal compressor 1 according to the embodiment of thepresent invention, showing the vicinity of an outlet section 22 b of animpeller 22F.

FIG. 4 is an enlarged cross-sectional view of major parts of themulti-stage centrifugal compressor 1 according to the embodiment of thepresent invention, showing a cross-sectional view taken along line II-IIof FIG. 2.

FIG. 5 is an enlarged cross-sectional view showing major parts of afirst variant of the multi-stage centrifugal compressor 1 according tothe embodiment of the present invention.

FIG. 6 is an enlarged cross-sectional view showing major parts of asecond variant of the multi-stage centrifugal compressor 1 according tothe embodiment of the present invention.

FIG. 7 is an enlarged view showing major parts of a seal structure 50 a,which is a variant of a seal structure 50 according to the embodiment ofthe present invention.

FIG. 8 is an enlarged view showing major parts of a seal structure 60 a,which is a variant of a seal structure 60 according to the embodiment ofthe present invention.

FIG. 9 is an enlarged cross-sectional view showing major parts of anexample to which the seal structure 50 a and the seal structure 60 a areapplied, in the multi-stage centrifugal compressor 1 according to theembodiment of the present invention.

FIG. 10 is an enlarged cross-sectional view showing major parts of anexample to which the seal structure 50 and the seal structure 60 a areapplied, in the multi-stage centrifugal compressor 1 according to theembodiment of the present invention.

FIG. 11 is an enlarged cross-sectional view showing major parts of anexample to which the seal structure 50 a and the seal structure 60 areapplied, in the multi-stage centrifugal compressor 1 according to theembodiment of the present invention.

MODES FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be describedwith reference to the accompanying drawings. In addition, in thedrawings used for the following description, in order to make eachmember or component recognizable, the scale of each member may beappropriately varied.

(Centrifugal Compressor)

FIG. 1 is a schematic cross-sectional view of a multi-stage centrifugalcompressor (centrifugal compressor) 1 according to an embodiment of thepresent invention, and FIG. 2 is an enlarged view of a major portion Iof FIG. 1.

As shown in FIG. 1, the multi-stage centrifugal compressor 1 includes astationary body 10 having a casing 11 and a plurality of diaphragms 12(12A to 12F), 13 (13A to 13E), and 14 (14A and 1413), and a rotary body20 having a rotary shaft 21 and a plurality of impellers 22 (22A to22F).

In addition, an extending direction of an axis P (a central axis of therotary shaft 21) of the multi-stage centrifugal compressor 1 is simplyreferred to as “an axial direction.”

As shown in FIG. 1, the casing 11 has a tubular shape, an axis of whichoverlaps the axis P.

The casing 11 has opening sections 11 a formed at both ends in an axialdirection thereof, which are closed by the diaphragm 14A and thediaphragm 14B, respectively. The casing 11 has an introduction section11 c formed at one end side in the axial direction and through which aworking gas (fluid) G is introduced from the outside, and an ejectionsection 11 d formed at the other end side in the axial direction andthrough which the working gas G is ejected to the outside.

The casing 11 accommodates the diaphragms 12 (12A to 12F) and 13 (13A to13E) therein.

As shown in FIG. 1, the diaphragms (inner partition walls) 12A to 12Eand 13A to 13E partition impeller accommodating chambers 17A to 17E,which form pairs, and a portion of a flow path of a mainstream of theworking gas G. In addition, the diaphragm 12F partitions an impelleraccommodating chamber 17F and a portion of the flow path of themainstream with the diaphragm 14B.

In the description, the diaphragms 12 and 13 that form a pair aredesignated by the same letter, and the diaphragms 12 and 13 and theimpeller accommodating chamber 17 having an accommodating/to beaccommodated relationship are designated by the same letter as theimpeller 22.

As shown in FIG. 1, the diaphragms 12A to 12E are annular disc-shapedmembers, and an accommodating recess section 12 a is formed at a centralside of the other end surface (the other side in the axial direction)(see FIG. 2). A diameter-reducing recess section 12 b formed to conformto a shape of a shroud 25 of the impellers 22A to 22E is more deeplyformed at a central side of the accommodating recess section 12 a of thediaphragms 12A to 12E.

In addition, the diaphragm 12F is an annular disc-shaped member, and thediameter-reducing recess section 12 b formed to conform to the shape ofthe shroud 25 of the impeller 22F is formed at a central side of theother end surface (the other side in the axial direction).

As shown in FIG. 1, the diaphragms 12A to 12F are in continuous contactwith each other and accommodated in the axial direction in a state inwhich the diameter-reducing recess sections 12 b thereof are directed tothe other side in the axial direction.

The diaphragms 13A to 13E are annular disc-shaped members having asmaller diameter than the diaphragms 12A to 12E, and circular recesssections 13 a are formed at one end surfaces thereof (one side in theaxial direction) (see FIG. 2). The diaphragms 13A to 13E areaccommodated in the accommodating recess sections 12 a of the diaphragms12A to 12E, which form pairs, in the coaxial shape. In this state, thediaphragms 13A to 13E form a gap at the diaphragms 12A to 12E topartition a flow path, and the circular recess section 13 a is directedtoward the diameter-reducing recess section 12 b to partition theimpeller accommodating chambers 17A to 17E.

Similarly, in the diaphragm 14B formed of an annular disc-shaped member,a circular recess section 14 a is formed at a central side of one endsurface (one side in the axial direction), and the circular recesssection 14 a is directed to the diameter-reducing recess section 12 b ofthe diaphragm 12F to partition the impeller accommodating chamber 17F.In addition, a disposition space of a balance piston 26 (to be describedlater) is formed at a central side of the circular recess section 14 a.

As shown in FIG. 1, a journal bearing 16 a and a thrust bearing 16 b aredisposed at the diaphragm (end partition wall) 14A, the journal bearing16 a is disposed at the diaphragm (end partition wall) 1413, and thebearings rotatably support the rotary shaft 21.

(Rotary Body)

As shown in FIG. 1, the rotary shaft 21 is inserted through the casing11 and the diaphragms 12A to 12F and 13A to 13E, and the diaphragms 14Aand 14B, and rotatably supported about the axis P.

The balance piston 26 is disposed at the other end side of the rotaryshaft 21.

As shown in FIG. 1, six impellers 22A to 22F are installed at the rotaryshaft 21 in the axial direction at intervals, and are accommodated inthe above-mentioned impeller accommodating chambers 17A to 17F,respectively.

As shown in FIG. 2, each of the impellers 22 includes a disc-shaped hub23, a plurality of blades 24, and the shroud 25. The hub 23 is graduallyincreased in diameter from an inlet section 22 a to an outlet section 22b of the working gas G. The blades 24 radially extend from an outercircumference of the hub 23, and the shrouds 25 cover outercircumferential ends of the blades 24.

(Flow Path)

As shown in FIG. 1, in the multi-stage centrifugal compressor 1constituted by the above-mentioned configuration, the two impellers 22adjacent to each other in the axial direction are connected to aU-shaped flow path 15. In addition, the inlet section 22 a of theimpeller 22A of a first stage is in communication with the introductionsection 11 c of the casing 11, and the outlet section 22 b of theimpeller 22F of the final stage is in communication with the ejectionsection 11 d of the casing 11 (see FIG. 1).

As shown in FIG. 1, the U-shaped flow path 15 is partitioned as thediaphragm 13 forms a gap at the diaphragm 12 and the neighboringdiaphragm 12, which form a pair.

As shown in FIG. 2, the U-shaped flow path 15 includes a diffusersection 15 a, a return bend section 15 b, and a return section 15 c. Thediffuser section 15 a is connected to the outlet section 22 b of theimpeller 22, and velocity energy of the mainstream of the working gas Gdischarged from the impeller 22 is converted into pressure energy. Thereturn bend section 15 b is continuously formed at a downstream side ofthe diffuser section 15 a, and reverses a direction of the mainstreamflowing toward an outer circumferential side in the radial direction tobe directed to a center in the radial direction. The return section 15 cis continuously formed at a downstream side of the return bend section15 b, and introduces the mainstream into the impeller 22 of thedownstream side.

(First Clearance, Second Clearance)

In the multi-stage centrifugal compressor 1 formed of theabove-mentioned configuration, as shown in FIG. 2, a first clearance(clearance, a first clearance) 31 configured to avoid contact betweenthe shroud 25 and the diaphragm 12 is formed between the shroud 25 ofthe impeller 22 and the diaphragm 12.

As shown in FIG. 2, the first clearance 31 extends from an upstream sideopening 31 a opened in the radial direction at the upstream side of theinlet section 22 a of the impeller 22 to a downstream side opening 31 bopened in the axial direction at the downstream side of the outletsection 22 b of the impeller 22, and is formed in a curved shape whenseen in a cross-sectional view. More specifically, after extending fromthe upstream side opening 31 a to the outer circumferential side in theradial direction, the first clearance 31 is gradually increased indiameter along the shroud 25 and extends to the other side in the axialdirection to the downstream side opening 31 b.

Similarly, a second clearance (clearance, a second clearance) 32 isformed between the hub 23 of the impeller 22F of the final stage, therotary shaft 21, the balance piston 26, and the diaphragm 14B.

The second clearance 32 extends from an inner opening 32 b opened in theaxial direction at the downstream side of the outlet section 22 b in theimpeller 22F of the final stage to an outer opening 32 a incommunication with the outside of the casing 11, and has a curved shapewhen seen in a cross-sectional view. More specifically, after extendingfrom the inner opening 32 b to the other side in the axial direction,the second clearance 32 is bent after extending along the hub 23 and thediaphragm 14B to a central side in the radial direction, extends alongthe balance piston 26 and the diaphragm 14B to the other side in theaxial direction, and comes in communication with the outer opening 32 a.

(Seal Structure)

The multi-stage centrifugal compressor 1 has a seal structure 50 and aseal structure 60 configured to seal the first clearance 31 and thesecond clearance 32. In addition, in FIG. 1, illustration of the sealstructures 50 and 60 is omitted.

The seal structure 50 includes a labyrinth seal (seal member) 51A, and ashifting member 52A.

The labyrinth seal 51A is constituted by a plurality of annular finmembers fixed to the diaphragm 12. The labyrinth seal 51A is disposed atthe downstream side opening 31 b side of a portion of the firstclearance 31, which is gradually increased in diameter along the shroud25. In the labyrinth seal 51A, each of the fin members extends from thediaphragm 12 toward the central side in the radial direction, and amicro gap in the radial direction is formed between a tip of each of thefin members and the shroud 25.

FIG. 3 is an enlarged cross-sectional view of major parts of FIG. 2, andFIG. 4 is a cross-sectional view taken along line II-II of FIG. 2. InFIG. 4, illustration of the labyrinth seal 51A is omitted.

The shifting member 52A is an annular member, which is disposed at aportion (a gas inlet section 31 c) of the first clearance 31 extendingfrom the downstream side opening 31 b to one side in the axial direction(see FIG. 3). That is, as shown in FIGS. 3 and 4, the shifting member52A is disposed at a position of the first clearance 31 at which theshroud 25 of the impeller 22 and the diaphragm 12 oppose each other inthe radial direction.

The shifting member 52A has a passage block section 53 formed at theimpeller 22 side (an outer circumferential side), and a shifting section54 formed at the diaphragm 12 side (an inner circumferential side).

The passage block section 53 is continuously formed at the shiftingsection 54, extends from the shifting section 54 toward the shroud 25 ofthe impeller 22, and forms a micro gap in the radial direction betweenone tip having a sharp shape and the shroud 25.

The outer circumferential side of the shifting section 54, as shown inFIG. 3, is fixed to the diaphragm 12, and as shown in FIG. 4, aplurality of through-holes 55 passing through the mainstream side andthe labyrinth seal 51A are formed in the shifting section 54. Theplurality of through-holes 55 are perforated at equal intervals in thecircumferential direction.

As shown in FIG. 4, each of the through-holes 55 has a circularcross-sectional shape, and straightly extends from an aperture 55 a ofthe mainstream side to an aperture 55 b of the labyrinth side. Inaddition, the through-holes 55 are formed at a position at which theaperture 55 b of the labyrinth seal 51A side is slightly deviated in areverse direction of a normal rotational direction with respect to theaperture 55 a of the mainstream side. In addition, while thethrough-holes 55 of FIG. 3 should be shown by dotted lines inherently,for the purpose of easy understanding, the through-holes are shown bysolid lines.

The seal structure 60 includes a labyrinth seal (seal member) 51B and ashifting member 52B.

As shown in FIG. 2, a labyrinth seal 51B has the same configuration asthe labyrinth seal 51A, is fixed to an outer circumference of thebalance piston 26, and forms a micro gap in the radial direction betweentips of the plurality of annular fin members extending from the balancepiston 26 to the diaphragm 14B and the diaphragm 14B.

As shown in FIG. 3, the shifting member 52B has the same configurationas the shifting member 52A, and as shown in FIG. 2, is disposed at aportion (a gas inlet section 32 c) of the second clearance 32 extendingfrom the inner opening 32 b to the other side in the axial direction.That is, the shifting member 52B is disposed at a position of the secondclearance 32 at which the impeller 22F and the diaphragm 14B oppose eachother in the radial direction of the impeller 22F.

Next, an exciting force reducing operation of the seal structures 50 and60 having the above-mentioned configuration will be described withreference to the accompanying drawings.

As shown in FIG. 1, when the rotary body 20 is rotated, the working gasG flowed from the introduction section 11 c alternately flows throughthe impellers 22A to 22F and the U-shaped flow path 15 to be compressedstepwise, and the working gas G which reaches a high pressure is ejectedfrom the ejection section 11 d to the outside.

In the mainstream passing through the impeller 22, since velocity energyand pressure energy are applied by rotation of the impeller 22, apressure after discharge from the impeller 22 becomes high in comparisonwith a pressure before introduction into the impeller 22, and a pressuregradient occurs in the downstream side opening 31 b and the upstreamside opening 31 a of the first clearance 31.

For this reason, some of the working gas G in the mainstream dischargedfrom the impeller 22 is flowed into the first clearance 31 via thedownstream side opening 31 b and the shifting member 52A. Then, theworking gas G flowed into the first clearance 31 is divided into a highpressure side and a low pressure side as the passage to the upstreamside opening 31 a side is blocked by the labyrinth seal 51A.

Here, when the working gas G is flowed into the first clearance 31, asshown in FIG. 3, the passage block section 53 of the shifting member 52Aforms a micro gap with the shroud 25 of the impeller 22 and blocks thepassage of the working gas G. For this reason, the working gas G passesthrough the through-hole 55 of the shifting section 54 and flows intothe first clearance 31.

Here, while the working gas G discharged from the impeller 22 has avelocity component in the normal rotational direction by rotation of theimpeller 22, a velocity component in a reverse direction of the normalrotational direction is applied by passing the through-hole 55 of theshifting section 54. More specifically, a velocity component in thereverse direction with respect to a tangential vector in the normalrotational direction is applied.

As a result, the velocity component in the normal rotational directionof the working gas G is negated and reduced.

The working gas G passing through the shifting member 52A flows throughthe first clearance 31 to arrive at the labyrinth seal 51A.

Here, since the velocity component in the normal rotational direction ofthe working gas G is negated and reduced, an exciting force applied tothe rotary body 20 by the working gas G flowing through the firstclearance 31 is slight.

Further, since the velocity component in the normal rotational directionof the working gas G arriving at the labyrinth seal 51A is reduced, anexciting force applied to the rotary body 20 by the working gas Gflowing through the labyrinth seal 51 A is slight.

Additionally, since the mainstream (see FIG. 3) of the working gas Gpassing through the impeller 22F of the final stage reaches a higherpressure than the atmospheric pressure, a pressure gradient is generatedat the inner opening 32 b and the outer opening 32 a of the secondclearance 32, and the working gas G flows into the second clearance 32via the inner opening 32 b and the shifting member 52B.

The working gas G flowing into the second clearance 32 passes throughthe through-hole 55 of the shifting section 54 to flow into the secondclearance 32, the velocity component in the reverse direction of thenormal rotational direction is applied, and thus, the velocity componentin the normal rotational direction is negated and reduced (see FIGS. 2and 3).

The working gas G passing through the shifting member 5213 flows throughthe second clearance 32 to arrive at the labyrinth seal 51B.

Here, since the velocity component in the normal rotational direction ofthe working gas G is negated and reduced, an exciting force applied tothe rotary body 20 by the working gas G flowing through the secondclearance 32 is slight.

Further, since the velocity component in the normal rotational directionof the working gas G arriving at the labyrinth seal 51B is reduced, anexciting force applied to the rotary body 20 by the working gas Gpassing through the labyrinth seal 51B is slight.

As described above, according to the seal structures 50 and 60, sincethe shifting members 52A and 52B configured to allow passage of theworking gas G and reduce the velocity component in the normal rotationaldirection are provided, the velocity component in the normal rotationaldirection of the working gas G passing through the shifting members 52Aand 5213 and arriving at the labyrinth seals 51A and 51B is reduced.Accordingly, since the velocity component in the normal rotationaldirection of the working gas G passing through the labyrinth seals 51Aand 51B is reduced, an exciting force applied to the rotary body 20 canbe suppressed.

Further, since the exciting force applied to the rotary body 20 issuppressed by installing the shifting members 52 (52A and 52B), incomparison with the case in which the passage of the working gas G isformed at the diaphragms 12 and 14B, the configuration can be simplifiedand effort needed for the processing can be reduced.

In addition, when the passage of the working gas G is formed and theworking gas G having a high pressure is supplied to the labyrinth seals51A and 51B to reduce the velocity component in the normal rotationaldirection of the working gas G, since a differential pressure betweenthe high pressure side and the low pressure side of the working gas Gdivided by the labyrinth seals 51A and 51B is increased, an amount ofthe working gas G passing through the labyrinth seals 51A and 51B isincreased. According to the seal structures 50 and 60, since thedifferential pressure is reduced in comparison with the case in whichthe high pressure working gas G is supplied to the labyrinth seals 51 Aand 51 B, the working gas G passing through the labyrinth seals 51 A and51B can be suppressed to a small amount. Accordingly, volumetricefficiency can be maintained to favorably maintain efficiency of themulti-stage centrifugal compressor 1.

In addition, since the shifting members 52A and 52B apply the velocitycomponent in the reverse direction of the normal rotational direction tothe working gas G, the velocity component in the normal rotationaldirection of the working gas G can be further reduced, and the excitingforce applied to the rotary body 20 can be further suppressed.

Further, the shifting members 52A and 52B are installed at gas inletsections 31 c and 32 c into which the working gas G flows from themainstream side to the first clearance 31 and the second clearance 32.Here, as the velocity component in the normal rotational direction isreduced when the working gas G flows into the first clearance 31 and thesecond clearance 32, the velocity component in the normal rotationaldirection of the working gas G from the gas inlet sections 31 c and 32 ctoward the labyrinth seals 51A and 51B is reduced. Accordingly, theexciting force generated when the working gas G having the velocitycomponent in the normal rotational direction is directed from the gasinlet sections 31 c and 32 c toward the labyrinth seals 51A and 51B, andthe exciting force generated when passing through the labyrinth seals51A and 51B are reduced. Accordingly, the exciting force applied to therotary body 20 can be largely suppressed.

In addition, since the shifting members 52A and 52B are installed at thediaphragms 12 and 14B, necessity of adjusting a rotational balance ofthe rotary body 20 like the case in which the shifting members 52A and52B are installed at the impeller 22 is removed, and an effort neededfor the processing can be further reduced.

Further, since the shifting members 52A and 52B include the passageblock section 53 configured to block the passage of the working gas G,and the shifting section 54 having the through-hole 55 passing throughthe mainstream side and the side of the labyrinth seals 51A and 51B, theconfiguration of the shifting members 52A and 52B can be furthersimplified.

In addition, since the aperture 55 a of the mainstream side is slightlydeviated in the reverse direction of the rotational direction withrespect to the aperture 55 b of the side of the labyrinth seals 51A and51B, the through-hole 55 can apply the velocity component in the reversedirection of the normal rotational direction to the working gas G.

Further, since the shifting member 52A is installed at a position atwhich the impeller 22 and the diaphragm 12 of the first clearance 31oppose each other in the radial direction, when a relative displacementin the radial direction of the impeller 22 and the diaphragm 12 due to acentrifugal force or heat growth is smaller than that in the axialdirection due to a thrust force or heat growth, probability of contactof the shifting member 52A with the impeller 22 can be reduced.

In addition, in comparison with the case in which the shifting member52A is installed at a position at which the impeller 22 and thediaphragm 12 oppose each other in the axial direction, a relativeposition between the shifting member 52A and the impeller 22 disposed atthe diaphragm 12 upon assembly can be easily determined, andmanufacturing effort can be reduced.

Similarly, since the shifting member 52B is installed at a position ofthe second clearance 32 at which the impeller 22F and the diaphragm 14Boppose each other in the radial direction, the same effects as theabove-mentioned effect can be obtained.

In the above-mentioned configuration, while the seal structure 50 isapplied to the first clearance 31 and the seal structure 60 is appliedto the second clearance 32, any one of the seal structures 50 and 60 maybe omitted so that only the seal structure 50 may be applied as shown inFIG. 5 or only the seal structure 60 may be applied as shown in FIG. 6.

FIG. 7 is an enlarged view showing major parts of the seal structure 50a, which is a variant of the seal structure 50.

The seal structure 50 a has a different disposition place of theshifting member 52A from the seal structure 50. Specifically, while theshifting member 52A is disposed at a position of the first clearance 31at which the shroud 25 of the impeller 22 and the diaphragm 12 opposeeach other in the radial direction in the seal structure 50, incontrast, the shifting member 52A is disposed at a position of the firstclearance 31 at which the shroud 25 of the impeller 22 the diaphragm 12oppose each other in the axial direction in the seal structure 50 a.

According to the seal structure 50 a, when a relative displacement inthe axial direction of the impeller 22 and the diaphragm 12 due to athrust force or heat growth is smaller than that in the radial directiondue to a centrifugal force or heat growth, probability of contact of theshifting member 52A with the impeller 22 can be reduced.

FIG. 8 is an enlarged view showing major parts of the seal structure 60a, which is a variant of the seal structure 60.

As shown in FIG. 8, while the shifting member 52B is disposed at aposition of the second clearance 32 at which the hub 23 of the impeller22 and the diaphragm 14B oppose each other in the radial direction inthe seal structure 60, in contrast, the shifting member 52B is disposedat a position of the second clearance 32 at which the hub 23 of theimpeller 22 and the diaphragm 14B oppose each other in the axialdirection in the seal structure 60 a.

Even according to the above-mentioned configuration, the sameconfiguration as the above-mentioned seal structure 50 a can beobtained.

FIGS. 9 to 11 are enlarged cross-sectional views showing major parts ofvariants of the seal structures 50 and 50 a and the seal structures 60and 60 a.

For example, in the above-mentioned configuration, while the sealstructure 50 is applied to the first clearance 31 and the seal structure60 is applied to the second clearance 32, as shown in FIG. 9, the sealstructure 50 a may be applied to the first clearance 31 and the sealstructure 60 a may be applied to the second clearance 32.

In addition, as shown in FIG. 10, the seal structure 50 may be appliedto the first clearance 31 and the seal structure 60 a may be applied tothe second clearance 32, and as shown in FIG. 11, the seal structure 50a may be applied to the first clearance 31 and the seal structure 60 maybe applied to the second clearance 32.

Further, an operation procedure, a shape or combination of thecomponents described in the embodiment is one example, and they may bevaried based on design requirements without departing from the scope ofthe present invention.

For example, in the above-mentioned embodiment, the shifting members 52Aand 52B apply the velocity component in the reverse direction of thenormal rotational direction to the working gas G. Here, when thevelocity component in the normal rotational direction is reduced, sincethe velocity component in the normal rotational direction of the workinggas G passing through the labyrinth seals 51A and 51B is reduced, anexciting force suppressing effect of the rotary body 20 can be obtained.

In addition, in the above-mentioned embodiment, while a cross-sectionalshape of the through-hole 55 is a circular shape, the cross-sectionalshape of the through-hole 55 may have an elliptical or polygonal shape.Similarly, the through-hole 55 may have a curved shape, not limited tothe straight shape.

Further, when seen in the axial direction, the through-hole 55 mayextend only in a rotational tangential direction. Furthermore, asdescribed above, when the velocity component in the normal rotationaldirection is reduced, since the exciting force suppressing effect of therotary body 20 can be obtained, the through-hole 55 may extend only inthe radial direction.

In addition, in the above-mentioned embodiment, while the shiftingmembers 52A and 52B are positioned at the downstream side opening 31 bside and the inner opening 32 b side, respectively, while disposed at ahigher pressure side of the working gas G than the labyrinth seals 51Aand 51B, the shifting members may be disposed at the upstream sideopening 31 a side and the outer opening 32 a side.

Further, positions of the labyrinth seals 51A and 51B may beappropriately varied.

Furthermore, in the above-mentioned embodiment, a tip of the passageblock section 53 formed in a sharp shape may be one or more.

In addition, in the above-mentioned embodiment, while the labyrinth sealis used as the seal member, the seal member may have anotherconfiguration, or a brush seal or a honeycomb seal, or a shaft sealmechanism in which thin plates are stacked in the circumferentialdirection may be used.

Further, in the above-mentioned embodiment, while the shifting members52A and 52B are disposed at the stationary body 10 side, the shiftingmembers 52A and 52B may be disposed at the rotary body 20 side.

Furthermore, in the above-mentioned embodiment, while the presentinvention is applied to the multi-stage centrifugal compressor 1, thepresent invention may be applied to a single stage centrifugalcompressor.

In addition, in the above-mentioned embodiment, while the seal structureaccording to the present invention is applied to the centrifugalcompressor, the seal structure may be applied to another fluid machine.

INDUSTRIAL APPLICABILITY

The present invention relates to a seal structure configured to seal aclearance with respect to a flow path defined by a rotary body rotatedabout a central shaft and through which a mainstream passes and astationary body disposed at the rotary body to form the clearancetherebetween, the seal structure including: a seal member installed atthe clearance and configured to divide a fluid introduced into theclearance from the mainstream into a high pressure side and a lowpressure side; and a shifting member installed at the high pressure sideof the fluid in the clearance and configured to allow passage of thefluid and reduce a velocity component in a rotational direction of therotary body in the velocity component of the fluid.

According to the present invention, since the fluid passes through theseal member in a state in which the velocity component in the normalrotational direction is reduced, an exciting force applied to the rotarybody can be suppressed.

DESCRIPTION OF REFERENCE NUMERALS

-   1 . . . multi-stage centrifugal compressor (centrifugal compressor)-   10 . . . stationary body-   11 . . . casing-   12 (12A to 12F) . . . diaphragm (inner partition wall)-   14 (14A, 14B) . . . diaphragm (end partition wall)-   20 . . . rotary body-   21 . . . rotary shaft-   22 (22A to 22F) . . . impeller-   23 . . . hub-   24 . . . blade-   25 . . . shroud-   31 . . . first clearance (clearance, first clearance)-   31 c, 32 c . . . gas inlet section (fluid inlet section)-   32 . . . second clearance (clearance, second clearance)-   50, 50 a, 60, 60 a . . . seal structure-   51A, 51B . . . labyrinth seal (seal member)-   52 (52A, 52B) . . . shifting member-   53 . . . passage block section-   54 . . . shifting section-   55 . . . through-hole-   55 a . . . aperture-   55 b . . . aperture-   G . . . working gas (fluid)-   P . . . central shaft

1. A seal structure for sealing a clearance between a rotary bodyrotated around an axis and a stationary body disposed adjacent to therotary body, in which a mainstream of a fluid passes through a passageformed by the rotary body and the stationary body, the seal structurecomprising: a seal member installed at the clearance and configured todivide a fluid flowed into the clearance from the mainstream into a highpressure fluid and a low pressure fluid; and a shifting member installedat an area of the high pressure fluid in the clearance, and configuredto allow passage of the fluid and reduce a velocity component in arotational direction of the rotary body in the velocity component of thefluid.
 2. The seal structure according to claim 1, wherein the shiftingmember applies a velocity component in a reverse direction of therotational direction to the fluid.
 3. The seal structure according toclaim 1, wherein the shifting member is installed at a fluid inletsection into which the fluid flows from the mainstream side to theclearance.
 4. The seal structure according to claim 1, wherein theshifting member is installed at the stationary body side.
 5. The sealstructure according to claim 4, wherein the shifting member has apassage block section formed at the rotary body side and configured toblock passage of the fluid, and a shifting section formed at thestationary body side, and having a through-hole passing through themainstream side and the seal member side and formed at a position atwhich an aperture of the mainstream side is slightly deviated in thereverse direction of the rotational direction with respect to anaperture of the seal member side.
 6. The seal structure according toclaim 1, wherein the shifting member is installed at a position of theclearance in which the rotary body and the stationary body oppose eachother in the radial direction of the rotary body.
 7. A centrifugalcompressor having a flow path defined by a rotary body and a stationarybody, wherein the rotary body includes an impeller having a disc-shapedhub, a plurality of blades extending from the hub, and a shroudconfigured to cover outer circumferential ends of the plurality ofblades, and the stationary body includes a casing configured toaccommodate the impeller, and an inner partition wall configured topartition the flow path into a low pressure side and a high pressureside of the mainstream, the centrifugal compressor including: a sealstructure according to claim 1, the seal structure configured to seal afirst clearance formed between the shroud of the impeller and the innerpartition wall.
 8. A centrifugal compressor having a flow path definedby a rotary body and a stationary body, wherein the rotary body includesan impeller having a disc-shaped hub and a plurality of blades extendingfrom the hub, and the stationary body includes a casing configured toaccommodate the impeller, and an end partition wall configured topartition the inside and the outside of the casing, the centrifugalcompressor including: a seal structure according to claim 1, the sealstructure configured to seal a second clearance formed between the hubof the impeller and the end partition wall.
 9. A centrifugal compressorhaving a flow path defined by a rotary body and a stationary body,wherein the rotary body includes an impeller having a disc-shaped hub, aplurality of blades extending from the hub, and a shroud configured tocover outer circumferential ends of the plurality of blades, and thestationary body includes a casing configured to accommodate theimpeller, an inner partition wall configured to partition the flow pathinto a low pressure side and a high pressure side of the mainstream, andan end partition wall configured to partition the inside and the outsideof the casing, the centrifugal compressor including: a seal structureaccording to claim 1, the seal structure configured to seal a firstclearance formed between the shroud of the impeller and the innerpartition wall, and a second clearance between the hub of the impellerand the end partition wall.
 10. The seal structure according to claim 2,wherein the shifting member is installed at a fluid inlet section intowhich the fluid flows from the mainstream side to the clearance.
 11. Theseal structure according to claim 2, wherein the shifting member isinstalled at the stationary body side.
 12. The seal structure accordingto claim 3, wherein the shifting member is installed at the stationarybody side.
 13. The seal structure according to claim 10, wherein theshifting member is installed at the stationary body side.
 14. The sealstructure according to claim 11, wherein the shifting member has apassage block section formed at the rotary body side and configured toblock passage of the fluid, and a shifting section formed at thestationary body side, and having a through-hole passing through themainstream side and the seal member side and formed at a position atwhich an aperture of the mainstream side is slightly deviated in thereverse direction of the rotational direction with respect to anaperture of the seal member side.
 15. The seal structure according toclaim 12, wherein the shifting member has a passage block section formedat the rotary body side and configured to block passage of the fluid,and a shifting section formed at the stationary body side, and having athrough-hole passing through the mainstream side and the seal memberside and formed at a position at which an aperture of the mainstreamside is slightly deviated in the reverse direction of the rotationaldirection with respect to an aperture of the seal member side.
 16. Theseal structure according to claim 13, wherein the shifting member has apassage block section formed at the rotary body side and configured toblock passage of the fluid, and a shifting section formed at thestationary body side, and having a through-hole passing through themainstream side and the seal member side and formed at a position atwhich an aperture of the mainstream side is slightly deviated in thereverse direction of the rotational direction with respect to anaperture of the seal member side.
 17. The seal structure according toclaim 2, wherein the shifting member is installed at a position of theclearance in which the rotary body and the stationary body oppose eachother in the radial direction of the rotary body.
 18. The seal structureaccording to claim 3, wherein the shifting member is installed at aposition of the clearance in which the rotary body and the stationarybody oppose each other in the radial direction of the rotary body. 19.The seal structure according to claim 4, wherein the shifting member isinstalled at a position of the clearance in which the rotary body andthe stationary body oppose each other in the radial direction of therotary body.
 20. The seal structure according to claim 5, wherein theshifting member is installed at a position of the clearance in which therotary body and the stationary body oppose each other in the radialdirection of the rotary body.